Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
  • H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
  • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
  • H04B7/2643—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile using time-division multiple access [TDMA]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
  • H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
  • H04W16/12—Fixed resource partitioning

Definitions

• the present invention relates to multi-cell wireless radio telecommunication systems and, more particularly, to indoor cellular radio telecommunication systems and radio network planning.
• Time Division Multiple Access (TDMA) radio communication systems such as microcell cellular radio communication systems operating in accordance with the Global System for Mobile communication (GSM), for example, comprise a plurality of radio access units or radio base stations. Each providing service to a relatively small area or cell , generally having a radius of 10-100 indoor and uptil 500 m outdoor.
• the radio access units operatively connect to a central interface unit, also called Radio Exchange (RE) or Base Station Controller (BSC) which, in turn, connects to a Private Automatic Branch exchange (PABX), the Public Switched Telephone Network (PSTN) or the Integrated Service Digital Network (ISDN), for example.
• PABX Private Automatic Branch exchange
• PSTN Public Switched Telephone Network
• ISDN Integrated Service Digital Network
• a duplex radio link can be established, generally occupying a pair of receive and transmit time slots grouped in a frame.
• a duplex radio link is established through a first time slot or transmission burst in a frame for downlink transmissions, i .e. from the radio access units to the remote radio communication devices, and a second time slot in the same frame for uplink transmissions, i.e. from the remote radio communication devices to the radio access units.
• a GSM frame comprises 8 time slots, providing 4 full- rate radio links per carrier.
• subrate transmission channels have been defined, the transmission capacity of which is a fraction of the transmission capacity of a full-rate time slot.
• Eight-rate traffic channels are specified and used for signalling, also called Stand-alone Dedicated Control CHannels (SDCCH).
• SDCCH Stand-alone Dedicated Control CHannels
• TDMA/FDMA Frequency Division Multiple Access
• the FDMA part involves the division by frequency of the Radio Frequency (RF) bandwidth into multiple carrier frequencies.
• RF Radio Frequency
• one or more carrier frequencies are assigned to each base station, and each of the carrier frequencies is divided in time using a TDMA scheme as disclosed above.
• GSM cordless and microcell cellular
• European patent application 0444841 likewise discloses a cellular radio system wherein time slots of a TDMA frame are fixedly or dynamically shared between adjacent sectors of a cell.
• TDMA Time Division Multiple Access
• radio access units or radio base stations arranged to provide duplex radio communication with remote radio communication devices in geographically limited areas or cells through a plurality of receive and transmit time slots grouped in frames, characterized in that the radio communication system is arranged to provide radio communication in a cell through a limited subset of the plurality of receive and transmit time slots of a frame.
• the system according to the invention limits the number of available receive and transmit time slots of a frame for communication in a particular cell, thereby providing for time slot planning instead of the well-known frequency planning widely used in GSM systems, for example.
• time slots can be more effectively occupied while simultaneous interfering transmissions of radio links between cells can be prevented by an appropriate choice of the available time slots per cell.
• the radiocommunication system is arranged to provide radio communication in neighbouring cells through different subsets of the plurality of receive and transmit time slots. Thereby effectively preventing interference between adjacent cells.
• radio communication in a cell is restricted to a limited subset of the plurality of receive and transmit time slots of frames of different carriers. That is, in a cell several subsets of receive and transmit time slots can be provided, transmitted at different RF carriers.
• the subsets of receive and transmit time slots available for radio communication in a cell can be adaptively selected or fixedly allocated.
• an arbitrary available subset of receive and transmit time slots is selected for communication in a cell.
• Subsets of receive and transmit time slots of a particular frame already in use in neighbouring cells are prevented from selection.
• the occupied time slots of a frame during use in a cell may differ from time to time.
• the radio communication devices can be designed for operation at the complete RF spectrum and time slots available for the radio communication system as a whole, such as with GSM, in order to provide handovers from one cell to another while the user of a radio communication device moves through the cells of the system.
• time slots 0 and 1 can be allocated to a first cell
• time slots 2 and 3 can be allocated to a second adjacent cell
• time slots 4 and 5 may be allocated to a third adjacent cell
• time slots 6 and 7 can be predeterminedly allocated to a fourth neighbouring cell. Radio communication in a particular cell is only possible through the time slots allocated to such cell.
• a subset of one pair of receive and transmit time slots of a frame is allocated to a cell .
• a subset of two pairs of receive and transmit time slots is allocated to a cell, in order to support inter and intra cell handovers.
• the radio communication system according to the invention can be operated in accordance with known TDMA protocols.
• the advantages of the present invention are best encountered if applied to a radio communication system operating following the GSM standard or equivalent.
• a GSM radio communication terminal operating in a conventional GSM network can also operate in an (indoor) microcell cellular GSM system arranged in accordance with the present invention.
• the restriction of information exchange to a predetermined subset of time slots in a cell can be completely controlled through the radio access units of the system.
• a cordless radio communication standard such as the Digital Enhanced Cordless Telecommunications (DECT) technology, for example.
• DECT Digital Enhanced Cordless Telecommunications
• both the radio access units and the remote radio communication devices are arranged to operate at ⁇ Jer low RF output power levels adapted for radio communication limited to pico cell or even nano cell ranges. That is cells having a radius of up to 10-15 metres. Contrary to the above-mentioned common approach for GSM systems, with the radio communication system according to the invention, in order to increase the communication capacity, the cell sizes are effectively decreased. With the above low RF output power levels, it appears sufficient to allocate 2 or 3 RF carriers of a GSM radio system, for example, for indoor services throughout the GSM network as a whole.
• a radio access unit comprises a wireless transmission interface operatively connecting to a wireless radio access controller and/or radio access exchange means.
• a wireless transmission interface operating in accordance with the DECT standard.
• the invention further provides a radio access unit and radio communication device particularly designed for use in a TDMA radio communication system and/or a method of duplex radio communication according to the present invention.
• Fig. 1 shows, in a schematic and illustrative manner, a typical cellular radio telecommunication system operating in accordance with the Global System for Mobile communications.
• Fig. 2 shows, in a schematic and illustrative manner, a typical TDMA frame and, in more detail, the organisation of a time slot.
• Fig. 3 shows, in a schematic and illustrative manner, a typical allocation of time slots in a radio communication system according to the present invention.
• Fig. 4 shows, in a schematic and illustrative manner, an embodiment of the radio communication according to the invention arranged for indoor usage.
• Fig.5 shows a simpl ified block diagram of an embodiment of a radio access unit operating in accordance with the present invention.
• Fig.6 shows a si pl ified block diagram of an embodiment of a remote radio communication device for operation in radio communication system according to the present invention.
• a cellular radio communication system such as a cellular radio communication system operating in accordance with the Global System for Mobile communications (GSM) standard.
• GSM Global System for Mobile communications
• the invention is generally applicable in Time Division Multiple Access (TDMA) radio communications systems both cellular and cordless radio communication systems, such as designated DCS 1800, PCS 1900, PDC, DECT, PHS, CT3 etc.
• Fig. 1 shows a typical architecture of a GSM network
• the GSM network 10 comprising several functional entities, the functions and interfaces of which are specified in applicable protocols.
• the GSM network 10 can be divided into three general parts.
• the radio access unit or radio base stations subsystem which controls the radio or Um-interface 16 with the mobile equipment 11.
• the main part of the radio base station subsystem is formed by a Base Station Controller (BSC) 14 and Base Transceiver Stations (BTSs) 15 which connect to the BSC 14.
• BSC Base Station Controller
• BTSs Base Transceiver Stations
• GSM network 10 A third and major part of the GSM network 10 is the network subsystem 20 comprising the Mobile services Switching Centre (MSC)
• MSC Mobile services Switching Centre
• PSTN Public Switched Telephone Network
• ISDN Integrated Services Digital Network
• the network subsystem 20 further comprises a Home Location Register (HLR) 22 and a Visitor Location Register (VLR) 23 which, together with the MSC 21, provide the call-routing and roaming capabil ities of the GSM network 10.
• the HLR 22 contains all the administrative information of each subscriber registered in the GSM network 10 and the current location of the mobile equipment 11.
• the VLR 23 contains selected administrative information from the HLR 22, necessary for call control and provision of the subscriber services for each mobile currently located in the geographically area controlled by the VLR 23.
• an Equipment Identity Register (EIR) 24 and an Authentication Centra (AuC) 25 are provided in the network subsystem 20.
• the EIR 24 is a data base containing a list of valid mobile equipment on the network 10 and the AuC 25 is a protected data base storing a copy of the secret key of each subscriber's SIM card 12.
• the MSC 21 connects to the BSC 14 through a so-called A- interface 18.
• the BTSs 15 connect to the BSC 18 across a so-called Abis- interface 19.
• Each BTS 15 provides service to a geographically limited area or cell 13.
• the cells 13 are arranged, such that a wide geographic area is completely covered by a plurality of adjacent cells 13.
• GSM operates following a combination of Time and Frequency Division Multiple Access (TDMA/FDMA) .
• the FDMA part involves the division by frequency of the available transmission bandwidth into a plurality of Radio Frequency (RF) carriers.
• RF Radio Frequency
• One or more carrier frequencies are assigned to each BTS 15, such that no or little interference occurs between communications in adjacent or neighbouring cells 13.
• RF Radio Frequency
• Each of the carriers is further divided in time, using a TDMA scheme as illustrated in fig. 2.
• the fundamental unit of time in the TDMA scheme of fig. 2 is called a burst period or time slot TO, Tl, ..., T7.
• Each time slot forms a physical or communication channel per TDMA frame.
• Duplex transmission between a BTS 15 and ME 11 comprises two time slots separated in time by 3 burst periods or time slots, so that the ME 11 does not have to transmit and receive simultaneously, thus simplifying the electronics.
• time slot T3 A typical bit organisation of a time slot is shown for time slot T3.
• the time slots in their data bits part, carry traffic from two different speech samples.
• both the MEs 11 and the BTSs 15 operate at a lowest power level that will maintain an acceptable signal quality.
• radio communication in a cell is limited to a subset of time slots of a frame.
• Fig. 3 shows a plurality of adjacent or neighbouring cells 30-35, each serviced by a radio access unit or radio base station 36-41, respectively.
• communication in each cell 30-35 is limited to one pair of receive and transmit time slots of a frame, i.e. for uplink and downlink transmissions between a radio access unit 36-41 and a remote radio communication device or ME 42, 43, 44 in a cell 30-35.
• communication of radio access unit 36 is limited to time slots TO and T4 at carrier frequency fl.
• Radio access unit 37 may communicate during time slots Tl and T5 of the frame at carrier fl.
• radio communication is possible during time slots T2 and T6 of the frame at carrier fl and radio access unit 39 communicates during time slots T3 and T7 of the frame at carrier frequency fl.
• radio communication is allowed during time slots TO and T4 of the frame at carrier frequency f2 whereas for cell 35 radio access unit 41 is arranged to communicate during time slots Tl and T5 of the frame at carrier frequency f2 etc.
• cells are created using time slot planning. Although operating at the same carrier frequency fl, ME 42 in cell 30 will not interfere with ME 43 in the adjacent cell 31.
• a subset of two or more pairs of receive and transmit time slots can be allocated to a particular cell or radio access unit on the same or different carriers.
• N pairs of time slots are allocated to a cell such that 1 ⁇ N ⁇ M.
• N 2 if intra and inter cell handovers between neighbouring cells have to be supported.
• one time slot of a subset of time slots allocated to a cell can be used as a control channel, while the other is used for communication purposes. If the first slot is in operation, and a call is set up on the second (control channel) time slots, than the control channel is converted to a communication channel or traffic channel . Next, the first time slot that is released is converted to a control channel again etc. In the case of fixedly allocated time slots, conversion of control and traffic or communication channels can be established if at least two pairs of receive and transmit time slots are allocated to a particular cell.
• fig. 3 shows an embodiment wherein frames at several carrier frequencies are available, it will be appreciated that this is not a prerequisite.
• non-adjacent cells can be operated at the same frequency and time slot pairs without unduly interfering eachother.
• a plurality of pico or nano cells can be created, each having its own radio access unit.
• the radio access units and remote radio communication devices are preferably installed, such that there is always nearly line of sight communication between a remote radio communication device and a radio access unit in a room or office module.
• the power amplifier in the remote communication device such as a cellular radio terminal, has to be switched off or reduced to low power.
• This can be achieved, following the invention, by applying appropriate RF control means in both the access units 36-41 and the mobile terminals.
• Fig. 4 shows a radio communication system 45 following the invention, installed in an office building comprising three floors, i.e. floor 1, floor 2 and floor 3. Each floor comprises a number of radio access units 46 associated with a cell 47. Further, at each floor one or a plurality of wireless radio access controllers 48 are provided, which connect to a local controller 49.
• the radio access units 46 comprise a wireless transmission interface 50 for communication with a radio access controller
• the radio access units 46 provide radio communication to remote radio communication devices 44 in a cell 47 via a wireless communication interface 51, e.g. following the GSM protocol.
• the wireless transmission interface 50 between the radio access units 46 and the radio access controllers 48 may be of any suitable type, preferably operating in accordance with the Digital Enhanced Cordless Telecommunications (DECT) standard.
• DECT Digital Enhanced Cordless Telecommunications
• DECT operates under a MC/TDMA/TDD (Multiple Carrier/Time Division Multiple Access/Time Division Duplex) protocol, wherein Dynamic Channel Allocation (DCA) is used for establishing radio links.
• DCA Dynamic Channel Allocation
• the local controller 49 connects to radio exchange means 52 of a radio access network, such as the BSC 14 of the GSM network 10 of fig. 1.
• the local controller 49 operates as a protocol converter between the GSM network on the one hand, and the radio access controllers 48, such as operating in accordance with the DECT protocol, on the other hand.
• the local controller 49 is arranged to emulate a BTS of the GSM network, such as the BTS 15 (figure 1).
• protocol conversion will include appropriate conversion of timing and control signals as well as adaptation of data bit rates and is regarded to be in the reach of persons skilled in the art.
• Handovers between base stations or radio access units 46 are controlled by the BSC 52 in the normal manner, following the GSM protocols, whereas instructions are converted in the protocol conversion part of the local controller 49.
• the radio access units 46 can be of a very simple type, having the size of a match box, and can be placed at an office desk or wall mounted. Through the radio interface 50 a wireless connection is provided with a radio access controller 48, providing a very easy and simple installation. In practice, a floor typically may be equipped with 30 to 50 or even more radio access units 46.
• the radio access units 46 may be arranged such to transmit through a fixed subset of full or sub-rate time slots of a frame.
• the local controller 49 adaptive selection of time slots can be achieved. That is, once a pair of time slots of a frame is occupied by a radio access unit 46, the local controller 49 prevents occupation of the same time slot pair in an adjacent cell.
• a GSM operator may allocate two or three radio frequencies particularly for microcell cellular systems for indoor and (limited) outdoor usage operating in accordance with the present invention.
• Those skilled in the art will appreciate that this a very advantage approach, in that by reserving such a limited number of frequencies for indoor usage in an overall GSM network, co-channel interference in pico and nano cells overlaid by a macro cell can be effectively avoided.
• a DECT transmission interface between the radio access units 46 and the radio access controllers 48 is preferred in view of the dynamic channel control algorithm of the DECT system, by which the radio access units 46 are connected "on demand", other transmission interfaces whether wired or wireless, such as a wired or wireless Local Area Network (LAN), can be used as well.
• LAN Local Area Network
• Fig.5 shows, in a simple block diagram, a radio access unit, such as a radio access unit 46, in accordance with the present invention.
• the transceiver part 55 may be arranged as a two-time slot, single carrier transceiver, operable at any time slot of a frame and any RF carrier available to a communication system or, a limited number of RF carriers, such as RF carriers particularly designated for indoor use, for example.
• a typical output power is 0.5 W for indoor use in pico- cell and nano cell environments.
• An extra receive function 56 is provided in order to monitor traffic at the air interface 51. Physically, this can be implemented with the receiver already used for communication purposes.
• Control means 57 provide a suitable algorithm, managing the selection of time slots and frequencies, as disclosed above.
• the control means 57 generally comprise a microprocessor or microcontroller.
• Transmission interface means 58, 59 preferably wireless transmission interface means 50 operating in accordance with the DECT protocol, operatively connects the radio access unit 46 through the intermediate radio access controller 48 to the local controller 49.
• the transmission interface 59 may also be designed for wired or wireless communication through a suitable LAN protocol, for example.
• Fig. 6 shows a block diagram of a remote communication device 44 for use with a radio communication system according to the invention, comprising transceiver means 61, control means 62 including a microprocessor or microcontroller and information exchange means 63.
• the information exchange means 63 may comprise, for example, a microphone and loudspeaker part for radio telephone purposes, display means, keyboard means and databus means.
• the control means may be arranged for communication at a limited subset of time slots of a TDMA frame or frames.
• RF control means 64 are provided, operatively connecting to the transceiver means for limiting the RF output power of the remote radio communication device 60 responding to a low power indoor radio communication system according to the invention.
• radio communication system is not limited to radio terminal devices having low RF output power, but can be used with conventional mobile radio telephones, such as GSM radio telephones, maintaining the advantages of improved indoor communication without requiring dual mode radio communication devices.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)

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• 1998
  • 1998-05-18 EP EP98201641A patent/EP0959636A1/de not_active Withdrawn
• 1999
  • 1999-04-29 WO PCT/EP1999/003034 patent/WO1999060808A1/en not_active Application Discontinuation
  • 1999-04-29 CA CA002332014A patent/CA2332014A1/en not_active Abandoned
  • 1999-04-29 EP EP99924874A patent/EP1080595A1/de not_active Withdrawn
  • 1999-04-29 CN CN99808774A patent/CN1309876A/zh active Pending
  • 1999-04-29 AU AU41381/99A patent/AU4138199A/en not_active Abandoned
  • 1999-05-17 US US09/312,704 patent/US6549531B1/en not_active Expired - Lifetime

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